Theoretical Investigation of the HOCO radical in the Ground Electronic State

M. Mladenovic (1)

1 MSME - Laboratoire de Modélisation et Simulation Multi Echelle

Hydrocarboxyl radical, HOCO, plays an important role in the reaction between hydroxyl radical and carbon monoxid, HO+CO→H+CO2, which provides the most common pathway for atmospheric depletion of both OH and CO and is the principle source of heat in hydrocarbon flames. Our primary interest in HOCO arises from the new spectroscopic information [Ref. 1], providing gas phase spectra of the cis-conformer for the first time. In the present work, the potential energy surface (PES) for HOCO for the ground electronic state (X 2A') was explored by means of the partially spin adapted coupled cluster RCCSD(T) method using the cc-pVQZ basis set. Ab initio calculations were designed such to cover the range of spectroscopic interest. Vibrational and rovibrational (J=0-4) energy levels are obtained by means of computational strategies based on the discrete variable representation [DVR6] and the (functional+pointwise) coordinate representations [DVR(+R)+FBR] together with contraction schemes resulting from several diagonalization/truncation steps [Refs. 2,3]. Rotational constants computed for the ground vibrational state of trans-HOCO and cis-HOCO are in good agreement with the experimental values. Several adiabatic projection schemes have been employed to characterize the vibrational levels and to study the relevance of the intermode coupling (vibrational mixing). Numerically exact vibrational transitions are also presented for the quartic force fields developed recently for trans-HOCO, cis-HOCO, and the cis-HOCO anion [Refs. 4,5]. Our results help to clear up a large discrepancy between previously reported vibrational perturbation theory (VPT) and vibrational configuration interaction (VCI) predictions for the torsional frequency. References: [1] T. Oyama, W. Funato, Y. Sumiyoshi, Y. Endo, J. Chem. Phys. 134, 174303, 2011 [2] M. Mladenović, J. Chem. Phys. 112, 1070, 2000 [3] M. Mladenović, Spectrochim. Acta, Part A, 58, 809, 2002 [4] R. C. Fortenberry, X. Huang, J. S. Francisco, T. D. Crawford, T. J. Lee, J. Chem. Phys. 135, 134301, 2011 [5] R. C. Fortenberry, X. Huang, J. S. Francisco, T. D. Crawford, T. J. Lee, J. Chem. Phys. 135, 214303, 2011

Domaines: Chimie théorique et/ou physique

M. Mladenovic. Theoretical Investigation of the HOCO radical in the Ground Electronic State. The 22nd International Conference on High Resolution Molecular Spectroscopy, Sep 2012, Prague, Czech Republic. pp.X, 2012. ⟨hal-00751396⟩